1. Field of Invention
This invention relates to sights for archery bows for use in hunting and tournament shooting, and more particularly to archery bow sights and sight mounts that include leveling devices that notify the archer when his shooting system is level.
2. Description of Prior Art
Sighting devices that use a leveling system when aiming a bow or archery shooting system are known and available for use in the art of archery. The leveling device is usually of the liquid filled glass tube type that relies on an air bubble suspended in the liquid to show when the leveling device is level. The leveling device is usually attached to the sight aperture so the archer can see both the level and the sighting index.
The leveling device allows the archer to assume that his bow is always perfectly vertical with respect to the longitudinal axis when he shoots the projectile (arrow) from the bow. Without the leveling device, the archer could lean or cant the bow to the left or right then causing the projectile to fly off course to the left or right.
Most archery bow sights have provisions for the adjustment of the sight aperture, that includes the leveling device, on the lateral and/or longitudinal axes. None have the capability to adjust the sight aperture about the vertical axis. This limitation is satisfactory as long as the bow is not going to be held in the uphill or downhill aiming position. However in most field archery tournaments and in hunting, uphill and downhill shooting is mandatory.
FIG. 4 shows the relationship of the vertical, lateral and longitudinal axes with respect to the archery bow.
FIG. 1 through FIG. 3 are diagrams that show the problems that arise if the sight aperture that includes the leveling device is not perpendicular (90 degrees) to the bow sight mounting arm with respect to the vertical axis when the bow is held in the uphill or downhill aiming position.
FIG. 1 shows what happens when the sight aperture and level are less than 90 degrees to the bow sight mounting arm with respect to the vertical axis. The archer draws his bow in the level position, looks at the sight aperture and sees the level as shown in FIG. 1b. At this point the bow is perfectly vertical and the level is indicating level. The archer then rotates his bow on the lateral axis and aims uphill. FIG. 1a shows what the level indicates to the archer when the bow is perfectly vertical about the longitudinal axis. Because the archer is relying on the level to notify him when his bow is perfectly level, he assumes that the level is correct, and rotates the bow about the longitudinal axis until the air bubble shows level. He has made the level indicate a level position, but in order to do this, he had to rotate the bow about the longitudinal axis and now the bow is not perfectly vertical but slightly canted to the right. This will cause the projectile to shoot slightly to the right. If the archer aims the bow downhill, the level will indicate what is shown in FIG. 1c. The same errors will occur as stated above only in reverse order.
FIG. 2 shows what happens when the sight aperture and level are greater than 90 degrees to the bow sight mounting arm with respect to the vertical axis. The archer draws his bow in the level position, looks at the sight aperture and sees the level as shown in FIG. 2b. At this point the bow is perfectly vertical and the level is indicating level. The archer then rotates his bow on the lateral axis and aims uphill. FIG. 2a shows what the level indicates to the archer when the bow is perfectly vertical about the longitudinal axis. Because the archer is relying on the level to notify him when his bow is perfectly level, he assumes that the level is correct, and rotates the bow about the longitudinal axis until the air bubble shows level. He has made the level indicate a level position, but in order to do this, he had to rotate the bow about the longitudinal axis and now the bow is not perfectly vertical but slightly canted to the left. This will cause the projectile to shoot slightly to the left. If the archer aims the bow downhill, the level will indicate what is shown in FIG. 2c. The same errors will occur as stated above only in reverse order.
FIG. 3 shows when the sight aperture is exactly 90 degrees to the bow sight mounting arm with respect to the vertical axis. Whether the archer is aiming the bow uphill, FIG. 3a, level, FIG. 3b, or downhill, FIG. 3c, the bow always stays perfectly level about the longitudinal axis.
Because there is no bow sight or bow sight mount available to satisfy the problems addressed above, the archer at the present time has to bend the threads on the sight aperture with needle nose pliers or other suitable tools, forward and backwards, until the aperture is 90 degrees to the bow sight mounting arm with respect to the vertical axis. This practice has several disadvantages such as:
1. The metal threads become brittle from bending them back and forth and break. PA1 2. Other adjustments made to the sight become out of alignment because of the stresses placed on them during the bending process. PA1 3. It is very difficult to adjust the sight exactly. PA1 4. The metal in the threads tends to seek its original position. PA1 5. The archer could slip with the tools and cause damage to the sight.